The present invention relates generally to electrical probing of integrated circuit packages and more specifically to a probe adapter for acquiring signals from solder ball connections of a Ball-Grid-Array package.
Surface mounted (SMT) integrated circuit devices have become the dominant type of IC packaging in the electronics industry. These device come in a wide variety of package configurations and lead pitch geometries. For example, IC packages may be square or rectangular with electrical contact or lead counts from 44 to 232 or higher. A variety of electrical contact or lead types are also being used. Quad flat pack IC's use Gull wing leads or J-leads. Both type of leads extend from the perimeter of the IC package with the former type of leads bending down and outward from the package while the later bend down and fold under the package in a J-shape. The leads are soldered to electrical contact pads formed on a circuit board. Pin-Grid-Array (PGA) and Ball-Grid-Array (BGA) devices have electrical contacts formed in a matrix on the bottom surface of the IC package. The PGA devices have lead wires extending downward that engage a corresponding matrix of through holes in the circuit board. The leads are soldered in the through holes to make the electrical connections. BGA devices have a matrix of electrical contacts formed on the bottom surface of the IC with solder balls formed on each contact, which allow soldering of the contacts to a corresponding matrix of electrical contact pads on the circuit board.
Probing PGA devices with standard measurement instrument electrical probes, such as passive and active oscilloscope probes or the like, requires access to the reverse side of the circuit board on which the PGA device is soldered. For BGA devices, additional contact pads have to be formed on the circuit board and electrically connected to the matrix of contact pads underneath the BGA device to allow probing of the device.
Another solution for probing electrical contacts of a BGA device is a probe adapter as described in U.S. Pat. No. 5,548,223 and assigned to Tektronix, Inc., assignee of instant invention. The probe adapter is made of a flexible dielectric material having electrical contacts formed in a central region that correspond to the electrical contacts on the BGA device. Extending outward from the central region of the adapter are wings on which are formed conductive runs that extend from each of the electrical contacts in the central region to electrical contacts formed at the periphery of the wings. The central region of the adapter is positioned between the BGA device and the substrate or circuit board and soldered in place using the solder balls of the BGA device. Such an adapter is intended for use in troubleshooting and debugging prototype circuit designs but not intended for troubleshooting circuits in production circuit boards or failed circuits boards in products.
What is needed is a probe adapter that allows electrical probing of individual solder ball connections of a mounted Ball-Grid-Array device.